Wall mounted designs.

[gafhenderson]

Wall mounted designs seem to sim very well for my in room conditions (carpets) BUT are there any pitfalls and problems that the simulations don't show that are prevalent in these types of designs?

If the edges are rounded and profiled so they almost seamlessly contact the wall boundaries, what will this do to baffle step?

Thanks for your help

An externally hosted image should be here but it was not working when we last tested it.

 

[tuxedocivic]

It's a great idea. I've been doing it for 6 months now and it's fantastic. It'll eliminate baffle step.

 

[guangui]

It's a great idea. I've been doing it for 6 months now and it's fantastic. It'll eliminate baffle step.

Do you have a pic or maybe opened a thread, that shows how it's done or how it looks?

 

[xrk971]

Wall mounts are about all I do. The advantage as you mentioned is no baffle step, you don't even need to round the edges. They also use the wall boundary to enhance the bass. Big advantage is no floorspace needed.

My wallmounts include:

1. Flat Folded mass loaded transmission line
2. Cornu spiral
3. Flat BIB or FIB

These are in the Foam Core thread, or the Terry Cain BIB thread. The Flat MLTL started out as a constant CSA Folded TL but I added a constricted vent to turn it to a MLTL and the bass now hits 55 Hz and is tight and punchy. All these designs are with the Vifa TC9FD driver.

The MLTL is best for smaller spaces, the cornu is good in medium or larger spaces, the FIB works anywhere and has the most bass.

Make wallmounts light weight so they can be hung anywhere. I use foam core and it works very well. excellent sound. Thin plywood works too.

MLTL

Cornu

FIB

 

[Scottmoose]

Short answer: yes, there can (can) be some issues that you won't see in Martin's worksheets since it's out of their intended purview. Arguably the most significant is that very shallow boxes may result in unwanted early reflections off the internal rear wall of the box & back through the cone. Which is 'annoying.' This is not invariable, varies depending on circumstances (some common sense helps: the Mk1 eyeball & realistic sense of proportion is as good a guide as you'll get), and may be ameliorated by careful damping. But in the worst cases, it's almost impossible to effectively counter short of making the box deeper. For similar reasons, very narrow boxes can have issues, except of couse there it's reflections from the internal side-walls.

 

[gafhenderson]

Short answer: yes, there can (can) be some issues that you won't see in Martin's worksheets since it's out of their intended purview. Arguably the most significant is that very shallow boxes may result in unwanted early reflections off the internal rear wall of the box & back through the cone. Which is 'annoying.' This is not invariable, varies depending on circumstances (some common sense helps: the Mk1 eyeball & realistic sense of proportion is as good a guide as you'll get), and may be ameliorated by careful damping. But in the worst cases, it's almost impossible to effectively counter short of making the box deeper. For similar reasons, very narrow boxes can have issues, except of couse there it's reflections from the internal side-walls.

i was planning on using an 'uneven' surface directly behind the driver (anechoic chamber-esque) to try and minimise this, or is this just wishful thinking?

 

[Overkill Audio]

Similar thread

Hi Guys,

The thread next door should be of interest, esp post number 110.

http://www.diyaudio.com/forums/full-range/191853-near-full-range-bmr-balanced-mode-radiator-11.html

With my on wall BMR line array, I have no sonic issues what so ever with baffle step, the sphere shape and 140mm ( under 6 inch's ) front to back depth eliminate it.
Re internal reflections, a very important issue indeed, much more so than baffle step IMO.
"For every action there is an equal reaction" so all that lovely room filling music energy you hear is only half the story... The same amount of energy is being generated backwards into the cabinet, and if you dont deal with it correctly it bounces around and is re-radiated back out through the cone...Out of Phase!
What we hear in the room includes some degree of unwanted rear wave, the more reflected rear wave we hear in room the worse the sound.
The total lack of out of phase internal reflections ( and reduced cabinet wall radiation) is the single biggest advantage of full open baffle designs.

It is best to combine different cabinet materials with different internal damping materials to best attenuate / dissapate the rear wave energy, each different material has a different resonance of its own and / or a different band of effective frequency attenuation. Also asymetrical internal walls are best.
Cheers
Derek.

 

[xrk971]

The back reflection is a good point, adding a conical deflector or roof shaped structure immediately behind driver helps as well as good amount of dense stuffing plus felt lining behind driver. I have not had a problem with it but have had problems with internal standing wave modes on the side walls as a resonator. You almost want to avoid building a rectangular prism shape (which of course is easiest to build). A trapezoidal shape or curves helps to break things up. Also internal bracing to break up the modes can also be used, as well as use of absorbent materials for internal walls like ceiling acoustic tiles for internal passages or walls.

 

[Overkill Audio]

Rear wave

Hi XRK,

I agree with your suggestions to help reduce back wave problems.
Your on wall spiral horn looks really cool.
One day I would like to try a BMR in a version of your spiral, at the moment I am full on with the on wall line array's, but hope to try it in the summer.

In advance of my experiments I have the following thoughts:

As the surface area of the spiral cabinet to Sd of driver is vast, it will be crucial to minimise cabinet resonance, esp the large front and rear baffle.
Making the front and rear from different materials will help distribute the energy more evenly ie avoid at using MDF on all panels.
As the BMR only weighs 250 grams (the good Neo magnet 4.5 inch one )and high panel rigidity is not required. this allows greater choice of materials ie a dense fibre board such as the under floor insulation panels?
If required one could strengthen the fibre board with a thin sheet, or even better, strips of, birch ply wood.
The internal spiral could be made from thin strips of an acoustically inert polymer / plastic, rebated into a shallow channel routed into the front / rear baffles, then glue filled and pushed together for final assembly.
All the best
Derek.

 

[xrk971]

Derek,
The foam core material is very nice for forming the inner channels of the Cornu spiral as it is easy to bend yet has sufficient rigidity to serve as the principal structural member between the front and rear baffles. Most people use either foam core or plywood or a combination of both for the front and rear baffles. It seems that the foam core provides some amount of inherent damping. I have proposed use of acoustic ceiling tiles for either one or both of the baffles and foam core for the channels. Rebating a channel on the baffles to tightly fit the spiral will make it very sturdy but adds complexity in the construction that we have avoided by simply using hot melt glue to tack sections of the spiral in place as it is curved and held by hand. This works amazingly well and is very easy to do as many folks in the Cornu thread can attest. I think the Cornu will work very well with a BMR and I have looked at the Tang Band flat honeycomb driver as an option. If aesthetics of wood are important, many people have glued a thin plywood veneer on top of the foam core baffle and this provides a disparate materials for sound absorption as well as makes it stronger for mounting the driver, and it looks good. There is no need to use anything thicker than 1/4 in plywood for these as light weight is important for hanging on walls. The other thing I ahve been contemplating is actually putting a very small class D amp board (like the Sure TPA3122 8W for $10) directly inside the wall hanging speakers so that only 12V or 19V DC from a wall wart or laptop PS brick plus a 3.5 mm plug for connecting to a music source.

I did not catch what brand and model of BMR driver you are using in your line arrays? They look very nice and I am sure sound great.

 

[Overkill Audio]

Foam core with veneer

Hiya,

I like the sound of adding a veneer of thin plywood for looks and sonics.
I have used fibre board a fair bit in the past and had good results so it will be interesting to experiment with it as well as foam core.
The hot melt glue and foam core sounds like it is pretty easy to build.
Just wish I had more hours in the day or days in the month!

I use the 4.5 inch (112mm square chassis) Neo magnet BMR. I have bought a large number as an OEM, but am getting through them fast as the array's use between 12 and 32 (!) drivers per pair!!
I am going to offer DIY Kits in a few months.
Cheers
Derek.

 

[tuxedocivic]

Build it "into" the wall. 6" deep wall with lots of fiberglass insulation does the trick.

I hear way less "box" with this setup than anything I've built. For the little 3" tang band in the left and right, 6" depth with damping material is plenty. And for the woofer, it stops at 300hz which the wavelength is just about where 6" could pose a problem, but does not.

 

[chrisb]

The only downsides I have pesronally experienced are

- not all rooms have sufficient wall space for symmetrical placement (both of mine are open plans with short pony walls, large windows and fireplaces etc, )

- seating locations for "critical" listening can be severely constrained (no so much an issue for home theater) -

There's no doubt of the advantages of lack of baffle step, no floor space consumed, and the opportunity for great artistic impression.
I can see these being particularly well suited for dedicated home theater application with projection systems, but the couple of in / on wall systems I've heard left something to be desired in terms of imaging and sense of depth and room ambience.

Now add the kind of equipment and furniture clutter that some of us have seen (Ryan - remember Dave's?), and ....

 

[Overkill Audio]

In wall Home Cinema

Hey Tux,

Nice job, I think in wall is a great solution for home cinema and very good for music.
Apart from the sonics / baffle step / free low frequency boost and perfect WAF, the real bonus is you can spend 90% of the speaker budget on the drivers...not the cabinet!

Add some mini DSP for crossovers if required, or just run mini array's of full ranger drivers and use a good AV reciever to crossover to corner placed subs... two or three 12 inch drivers is nice!
Even better use a good Oppo Blu Ray with onboard 32 Bit ESS DAC's as the source, run analog out to your own power amps. If you dont want to DIY power amp kits just buy a good 5 Ch power amp or even 5 stereo NAD, Cambridge Audio or any good value power amps.

Please dont let out the attack dogs.... But in my experience, and only once you reach the higher performance end of the scale, you will hear the benefit if you use good solid core speaker cable.
DIY - Use 0.8mm silver plated solid core copper, preferably single crystal high purity with 1 micron thick silver plating. Use crimps not solder where possible, and seal all joints with glue filled heat shrink covers.
Cover the cable with paper drinking straws or soft cotton sleeving, then cover in teflon tubing, then twist together and finally cover in heat shrink.
Use 0.4mm or 0.5mm for inter connects, Eichmann plugs are great.
Cheers
Derek.

 

[tuxedocivic]

Add some mini DSP for crossovers if required, or just run mini array's of full ranger drivers and use a good AV reciever to crossover to corner placed subs... two or three 12 inch drivers is nice!

You've got me pegged!

Changed a bit now, but 3" full range with 8" woofer FAST crossed over with a minidsp. A dual opposed 12" cab in the corner and 2 single 12 cabs placed strategically for room smoothing.

 

[Overkill Audio]

Great minds think alike!!

Hey Tux...We got it going on!

All the best
Derek.